Active Iron Powder And Heat Generating Body

ABSTRACT

There is provided an active iron powder which is suitable as a raw material of a heat generating body, is excellent in rising properties of a heat generating composition and is excellent in economy. The invention is concerned with an active iron powder to be contained in a heat generating composition capable of generating heat upon contact with air, characterized in that an amount of wustite to be contained in an iron powder is from 5.01 to 50% by weight in terms of an X-ray peak intensity ratio to iron.

TECHNICAL FIELD

The present invention relates to an active iron powder which is used ina heat generating body and to a heat generating composition and a heatgenerating body.

BACKGROUND ART

As products to be used by making air (oxygen) act on a mixture of aniron powder and a reaction aid, etc., in general, throwaway body warmersand so-called oxygen-free scavengers which are installed in a packagingbody of various foods and efficiently absorb oxygen in the packagingbody, thereby preserving the freshness of foods are well known.

As metal powders to be used in these products, an iron powder is themost general, and as the reaction aid, salt, water, and the like areused. It is also well known that as a water retaining agent for carryingsuch a substance thereon, active carbon, vermiculite, diatomaceousearth, a wood meal, a water absorptive polymer, and the like are mixedand used.

A role of the iron powder in a throwaway body warmer is to utilizereaction heat as generated due to oxidation, thereby achieving thepurpose. Accordingly, the performance of such a product is influenced bycharacteristics of the iron powder. In other words, if an iron powderhaving high activity is used, favorable products are produced.

In a throwaway body warmer, since what the temperature rises immediatelyafter breaking the seal enhances a product value, it is desired tosupply an iron powder having excellent exothermic rising characteristics(see, for example, Patent Documents 1 and 2).

Usually, in commercially available iron powders, the degree of reductionis strong, and the purity of iron is high. When used for a heatgenerating body, exothermic rising properties are insufficient, and itis attempted to improve the exothermic rising properties chiefly byadjusting the amount of addition of a carbon component such as activecarbon. However, satisfactory results have not been obtained yet in viewof the performance.

Then, an active iron powder whose surface has been modified by forming afixed amount of a thin film of a conductive carbonaceous substancelocally on the surface of an iron powder such that an oxidation reactionis promoted is known as a raw material for throwaway body warmers oroxygen-free scavengers.

[Patent Document 1] JP-A-53-60885

[Patent Document 2] JP-A-57-10673

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

However, according to the method for forming a fixed amount of a thinfilm of a conductive carbonaceous substance locally on the surface ofiron, though the exothermic rising properties of a heat generatingcomposition are improved, an effect thereof is insufficient, and aproduction step thereof becomes complicated. Thus, there was involved aproblem in view of costs.

An object of the invention is to provide an active iron powder which issuitable as a raw material of a heat generating body, is excellent inrising properties of a heat generating composition and is excellent ineconomy.

Means for Solving the Problems

The present inventors made extensive and intensive investigations,examined a production process of an iron powder and examined exothermicrising properties of a heat generating composition by treating a reducediron powder with an oxidizing gas and using various iron powders asprepared by changing their conditions and compounding, and the like.

As a result, it has been noted that in an iron powder having favorableexothermic rising properties of a heat generating composition, a wustitephase (FeO) is present. Then, as a result of examining an existent ratioof wustite and iron in terms of an X-ray peak intensity ratio, it hasbeen found that there is a relation in which when an intensity ratio ofwustite drops, the exothermic rising properties become worse and that ina sample wherein wustite is present, the exothermic rising propertiesare favorable.

As set forth in claim 1, an active iron powder of the invention is anactive iron powder to be contained in a heat generating compositioncapable of generating heat upon contact with air, which is characterizedin that an amount of wustite to be contained in an iron powder is from5.01 to 50% by weight in terms of an X-ray peak intensity ratio to iron.

Also, an active iron powder as set forth in claim 2 is characterized inthat in the active iron powder as set forth in claim 1, the active ironpowder is at least one member selected from a reduced iron powder, anatomized iron powder, and an iron powder comprising particles, a surfaceof each of which is at least partially covered by a conductivecarbonaceous substance.

As set forth in claim 3, a heat generating composition of the inventionis the heat generating composition as set forth in claim 1 containing asessential components containing an iron active powder according to claim1, a carbon component, a reaction accelerator and water, characterizedin that the active iron powder accounts for from 30 to 100% by weight ofthe iron powder in the heat generating composition.

As set forth in claim 4, a heat generating body of the invention ischaracterized by containing the heat generating composition as set forthin claim 3.

Also, the heat generating body as set forth in claim 5 is characterizedin that in the heat generating body as set forth in claim 4, the heatgenerating body has fixing means in at least a part thereof.

Also, the heat generating body as set forth in claim 6 is characterizedin that in the heat generating body as set forth in claim 5, the fixingmeans is an adhesive layer; and that the adhesive layer contains atleast one member selected from additional components consisting of awater retaining agent, a water absorptive polymer, a pH adjusting agent,a surfactant, an organosilicon compound, a hydrophobic polymer compound,a pyroelectric substance, an antioxidant, an aggregate, a fibrousmaterial, a moisturizer, a functional substance, and a mixture thereof.

ADVANTAGES OF THE INVENTION

As is clear from the foregoing description, by forming wustite at leaston the surface of an iron powder as produced by reduction of iron oxideor at least on the surface of a commercially available iron powder or aniron powder as produced as an intermediate stage product of processingand production such that an amount of wustite is from 5.01 to 50% byweight in terms of an X-ray peak intensity ratio to iron, an active ironpowder for heat generating body which is not only suitable as a rawmaterial of a heat generating body but also excellent in exothermicrising properties and excellent in economy is obtainable.

BEST MODES FOR CARRYING OUT THE INVENTION

The active iron powder of the invention is an active iron powder whichis contained in a heat generating composition capable of generating heatupon contact with air, in which an amount of wustite to be contained inan iron powder is from 5.01 to 50% by weight in terms of an X-ray peakintensity ratio to iron.

When the amount of wustite is large, a gas was generated so that therewas encountered a problem such that an outer bag which is anair-impermeable accommodating bag is swollen during the storage.However, by using a small amount of a hydrogen gas formation inhibitor,this problem was solved.

Examples of the iron powder include a cast iron powder, an atomized ironpowder, an electrolyzed iron powder, a reduced iron power, an ironpowder whose surface is partially covered by a conductive carbonaceoussubstance, and iron alloys thereof.

An X-ray analysis of a wustite phase was evaluated by using an X-raydiffraction device, and the amount of wustite was evaluated as a ratiobetween an integrated intensity of peaks on a (110) plane of iron and anintegrated intensity of peaks of a (220) plane of wustite.

In the invention, a wustite region is present at least one the surfaceof this iron powder, and an amount of wustite which is contained in theiron powder is from 5.01 to 50% by weight, preferably from 5.01 to 30%by weight, more preferably from 7 to 30% by weight, and furtherpreferably from 7 to 20% by weight in terms of an X-ray peak intensityratio to iron.

When the amount of wustite is less than 5.01% by weight, it isimpossible to contribute to the exothermic rising properties of a heatgenerating composition, whereas when it exceeds 50% by weight, a specialeffect is not promoted so that an exothermic time of a heat generatingcomposition or a heat generating body becomes short.

Furthermore, in the active iron powder of the invention, wustite and/oran iron oxide other than wustite may be present. Examples of the ironoxide include irons containing oxygen such as oxides, hydroxides andoxyhydroxides of iron.

Usually, in the reduced iron powder, the presence of wustite which is aniron oxide may possibly be formed due to air oxidation during thestorage, etc. However, the wustite fraction in such a state does notcontribute to the exothermic rising properties of a heat generatingcomposition.

By using the active iron powder of the invention as an iron powder forheat generating body, not only exothermic characteristics, especiallyinitial rising characteristics can be improved, but also the amounts ofa combustion improver and active carbon in the active components can bereduced.

That is, the invention is to use an iron powder which is generallyproduced at present and modify its function into an active iron powdersuitable as a raw material of a heat generating body.

The iron powder or active iron powder may contain a metal other thaniron, a semiconductor, and an oxide thereof.

The “iron alloy powder” as referred to herein is an iron alloy powdercontaining 50% or more of iron. The alloy component is not particularlylimited so far as it is a metal component including semiconductors otherthan iron and the iron component functions as a component of the heatgenerating composition. Examples thereof include silicon, zinc,aluminum, magnesium, manganese, nickel, and copper.

The iron powder may be an iron powder which contains a carbon componentand/or is partially covered by a carbon component.

In particular, an iron powder or an iron alloy powder wherein the ironcomponent is an iron powder or an iron alloy powder, the surface ofwhich is partially covered by from 0.3 to 3.0% by weight of a conductivecarbonaceous substance, is useful.

As the metal oxide other than iron oxide in the iron component whichcontains oxygen and/or is covered by oxygen, any substance may beemployed so far as it does not hinder the oxidation of iron by anoxidizing gas. Examples thereof include manganese dioxide and cupricoxide.

The heat generating composition contains, as essential components, aniron powder, a carbon component, a reaction accelerator and water, andthe active iron powder accounts for from 30 to 100% by weight of theiron powder in the heat generating composition.

As the water, one from a proper source may be employed. Its purity andkind and the like are not particularly limited.

In the case of the heat generating composition, the content of water ispreferably from 1 to 70% by weight, more preferably from 1 to 60% byweight, further preferably from 7 to 60% by weight, still furtherpreferably from 10 to 50% by weight, and even further preferably from 20to 30% by weight of the heat generating composition.

Furthermore, in the case of the reaction mixture or heat generatingmixture prior to the contact treatment with an oxidizing gas, thecontent of water is preferably from 0.5 to 20% by weight, morepreferably from 1 to 20% by weight, further preferably from 3 to 20% byweight, and still further preferably from 4 to 15% by weight of thereaction mixture or heat generating mixture.

The carbon component is not particularly limited so far as it containscarbon as a component. Examples thereof include carbon black, graphite,active carbon, carbon nanotubes, carbon nanohorns, and flullerenes.Carbon which has become conductive by doping or the like is alsoemployable. There are enumerated active carbons as prepared from coconutshell, wood, charcoal, coal, bone carbon, etc. and carbons as preparedfrom other raw materials such as animal products, natural gases, fats,oils, and resins. In particular, active carbons having an adsorptionretaining ability are preferable.

Furthermore, it is not always required that the carbon component ispresent alone. In the case where an iron powder containing the carboncomponent and/or covered by the carbon component is used in the heatgenerating composition, it is to be noted that the heat generatingcomposition contains the carbon component even though the carboncomponent is not present alone.

The reaction accelerator is not particularly limited so far as it isable to promote the reaction of the heat generating substance. Examplesthereof include metal halides, nitrates, acetates, carbonates, and metalsulfates. Examples of metal halides include sodium chloride, potassiumchloride, magnetic chloride, calcium chloride, ferrous chloride, ferricchloride, sodium bromide, potassium bromide, ferrous bromide, ferricbromide, sodium iodide, and potassium iodide. Examples of nitratesinclude sodium nitrate and potassium nitrate. Examples of acetatesinclude sodium acetate. Examples of carbonates include ferrouscarbonate. Examples of metal sulfates include potassium sulfate, sodiumsulfate, and ferrous sulfate.

The production process of an active iron powder according to theinvention is not limited so far as the amount of wustite to be containedin the iron powder can be controlled at from 5.01 to 50% by weight interms of an X-ray peak intensity ratio to iron. Examples thereof includea contact treatment with an oxidizing gas in which a reaction mixturehaving components of a heat generating composition mixed therein or aheat generating composition is brought into continuous or intermittentcontact with an oxidizing gas (for example, oxygen and air) in anoxidizing gas atmosphere or by blowing an oxidizing gas, or the like,thereby partially oxidizing the iron component.

A method for determining a degree of oxidation is not limited. Examplesthereof include a method of determining a degree of contact of thereaction mixture or heat generating composition with an oxidizing gas bya water mobility value of the reaction mixture or heat generatingcomposition, a contact time with an oxidizing gas, an exothermictemperature rise rate at the time of contact, an exothermic temperatureat the time of contact, a maximum exothermic temperature at the time ofcontact, a prescribed temperature as dropped after reaching a maximumexothermic temperature at the time of contact, or a combination thereof,thereby determining a degree of oxidation.

In addition, the following can be specifically enumerated.

1. A production process by reducing a mill scale or an ore to be used asa raw material of an iron powder at a temperature of not higher thanabout 1,300° C. by using a reducing agent such as hydrogen, charcoal,and coke, coarsely pulverizing the reduced cake by a hammer mill, a jawcrusher, etc., and then finely pulverizing it by a novorotor, apulverizer, or a vibration bowl.

2. A production process by reducing an iron powder containing an ironoxide, thereby producing a partially oxidized iron powder.

3. A production process of a heat generating mixture by subjecting areaction mixture of an iron powder, a reaction accelerator and water toa self-exothermic reaction in an oxidizing gas atmosphere to partiallyoxidize the iron powder, thereby containing an iron having an iron oxidefilm on the surface thereof.

4. A production process of a heat generating mixture by subjecting areaction mixture of an iron powder, a reaction accelerator, an acidicsubstance and water to a self-exothermic reaction in an oxidizing gasatmosphere.

5. A production process of a heat generating mixture by subjecting areaction mixture of an iron powder, a reaction accelerator, a carboncomponent and water to a self-exothermic reaction in an oxidizing gasatmosphere.

6. A production process of a heat generating mixture by subjecting areaction mixture of an iron powder, a reaction accelerator, an acidicsubstance, a carbon component and water to a self-exothermic reaction inan oxidizing gas atmosphere.

7. A production process of a heat generating mixture containing apartially oxidized iron powder by containing other component than theforegoing components in the reaction mixture or heat generating mixtureas set forth above in any one of 1 to 6 and carrying out the process asset forth above in any one of 1 to 6.

8. A production process of a heat generating mixture by carrying out theprocess as set forth above in any one of 1 to 7 under circumstanceswarmed at least 10° C. higher than the circumferential temperature.

9. A production process of a heat generating mixture by carrying out theprocess as set forth above in any one of 1 to 8 by blowing an oxidizinggas.

10. A production process of a heat generating mixture by carrying outthe process as set forth above in 9 by blowing an oxidizing gas warmedat least 10° C. higher than the circumferential temperature.

11. A production process of a heat generating composition by carryingout the contact treatment with an oxidizing gas in the process as setforth above in any of 1 to 10 until the temperature exceeds a maximumtemperature which is a maximum point of a temperature rise due to theexothermic reaction.

12. A production process of a heat generating mixture by carrying outthe contact treatment with an oxidizing gas in the process as set forthabove in any of 1 to 11 until the temperature exceeds a maximumtemperature due to the exothermic reaction and further drops by at least10 to 20° C. from the maximum temperature.

13. A production process of a heat generating composition by carryingout the contact treatment with an oxidizing gas in the process as setforth above in any of 1 to 11 until the temperature exceeds a maximumtemperature which is a maximum point of a temperature rise due to theexothermic reaction and after intercepting the oxidizing gas, holding ituntil at least the temperature of the reaction mixture drops by at least10 to 20° C. from the maximum temperature.

14. A production process of a heat generating mixture by treating thereaction mixture or heat generating mixture as set forth above in anyone of 1 to 7 under oxidizing gas circumstances by regulating atemperature rise at 1° C. or higher.

In addition, a heat generating mixture may be formed by adding othercomponents to the heat generating mixture and further carrying out thetreatment with an oxidizing gas.

Incidentally, the circumstances of the reaction mixture at the time ofthe contact treatment with an oxidizing gas are not limited so far asunder circumstances of 0° C. or higher, the reaction mixture is broughtinto contact with an oxidizing gas and a temperature rise of thereaction mixture is regulated at 1° C. or higher within 10 minutes.Examples thereof include a state that it is present in a vessel and astate that the reaction mixture is present in an air-permeablesheet-like material such as non-woven fabrics.

Furthermore, the contact treatment with an oxidizing gas may be carriedout with stirring or without stirring and additionally underfluidization or non-fluidization and may be carried out in a batchwisesystem or continuous system.

Here, with respect to the state of the reaction mixture at the time ofthe contact treatment with an oxidizing gas, so far as the amount ofwustite which is contained in the partially oxidized iron powder is from5.01 to 50% by weight in terms of an X-ray peak intensity ratio to iron,any of a standing state, a transfer state and a fluidizing state bystirring, etc. may be employed and properly selected. Furthermore,mixing of the respective components of the reaction mixture, heatgenerating mixture or heat generating composition and mixing at the timeof adjusting the water content may be achieved in an oxidizing gasatmosphere or by blowing an oxidizing gas.

The heat generating composition is not limited so far as it is a heatgenerating composition comprising an iron powder containing from 30 to100% of an active iron powder and other essential components or a heatgenerating composition further containing components other than theessential components.

Examples of the production process of the heat generating compositioninclude:

1) A production process by containing the active iron powder as producedby the process as set forth above in any one of 1 to 14 and theessential components other than the iron powder;

2) A production process by mixing the active iron powder as produced bythe process as set forth above in any one of 1 to 14 and the essentialcomponents other than the iron powder;

3) A production process by mixing the active iron powder as produced bythe process as set forth above in any one of 1 to 14 and an iron powderand further adding and mixing the essential components other than theiron powder; and

4) A process for producing a heat generating composition by adjustingthe water content of the composition as produced in 1) to 3) and mixing.

Incidentally, a production process of a heat generating composition bycontact treating a reaction mixture prepared by adding and mixing theessential components and other components with an oxidizing gas and thenadjusting the water content is especially preferable.

By using the active iron powder of the invention as an iron powder,exothermic rising characteristics of the heat generating composition areimproved so that it is possible to reduce the amount of a carboncomponent such as active carbon in the heat generating composition by 10to 20% or more. By reducing the amount of addition of the carboncomponent, it is possible to reduce costs.

Although a mechanism in which when the active iron powder of theinvention is used as an iron powder for heat generating body, theexothermic rising properties of the heat generating composition areimproved has not be elucidated in detail, it is assumed that because ofa catalytic effect of wustite against oxidation of iron and contactbetween an oxidizing gas and the components to cause oxidation of thecomponents, in particular, oxidation of an iron powder, not only an ironoxide film, i.e., an oxygen-containing film, is formed on the surface ofthe iron powder, but also the oxidized iron component is also adhered onthe surface of active carbon, whereby hydrophilicity is imparted orimproved on the both to cause coupling or structurization among thecomponents through the mediation of water. Furthermore, the case wheremagnetite (Fe₃O₄) is present in the iron oxide film is preferablebecause it is excellent in conductivity. The case where hematite (Fe₂O₃)is present in the iron oxide film is also preferable because it becomesporous.

It is preferable that the heat generating composition contains at leastone member selected from additional components consisting of a waterretaining agent, a water absorptive polymer, a pH adjusting agent, ahydrogen formation inhibitor, an aggregate, a fibrous material, afunctional substance, a surfactant, an organosilicon compound, apyroelectric substance, a moisturizer, a fertilizer component, ahydrophobic polymer compound, a heat generating aid, a metal other thaniron, a metal oxide other than iron oxide, an acidic substance, and amixture thereof.

The “water mobility value” as referred to herein is a value showing anamount of surplus water which can transfer to the outside of the heatgenerating composition in water present in the heat generatingcomposition. This water mobility value will be described below withreference to FIGS. 6 to 10.

As shown in FIG. 6, a filter paper 12 of No. 2 (second class of JISP3801) in which eight lines are drawn radiating from the central pointwith an interval of 45° is placed on a stainless steel plate 16 as shownin FIGS. 7 and 8; a template 13 having a size of 150 mm in length×100 mmin width and having a hollow cylindrical hole 14 having a size of 20 mmin inner diameter×8 mm in height is placed in the center of the filterpaper 12; a sample 15 is placed in the vicinity of the hollowcylindrical hole 14; and a stuffer plate 9 is moved on and along thetemplate 13 and inserted into the hollow cylindrical hole 14 whilestuffing the sample 15, thereby leveling the sample (force-in diemolding).

Next, as shown in FIG. 9, a non-water absorptive 70 μm-thickpolyethylene film 11 is placed so as to cover the hole 14, and a flatplate 16 made of stainless steel having a size of 5 mm in thickness×150mm in length×150 mm in width is further placed thereon and held for 5minutes such that an exothermic reaction is not caused.

Thereafter, a shown in FIG. 10, the filter paper 12 is taken out, and anoozed-out locus of the water or aqueous solution is read as a distance17 (unit: mm) from a periphery 18 as an edge of the hollow cylindricalhole to an oozed-out tip along the radiating lines. Similarly, adistance 17 from each of the lines is read, and eight values in totalare obtained. Each of the eight values (a, b, c, d, e, f, g and h) whichare read out is defined as a measured water content value. An arithmeticaverage value of the eight measured water content values is defined as awater content value (mm) of the sample.

Furthermore, the water content for the purpose of measuring a real watercontent value is defined as a compounded water content of the heatgenerating composition corresponding to the weight of the heatgenerating composition having a size of 20 mm in inner diameter×8 mm inheight or the like, similar measurement is conducted only with watercorresponding to that water content, and a value as calculated in thesame manner is defined as a real water content value (mm). A valueobtained by dividing the water content value by the real water contentvalue and then multiplying with 100 is a water mobility value.

That is, the water mobility value is represented by the followingexpression.(Water mobility value)={[Water content value (mm)]/[(Real water contentvalue (mm))]×100

With respect to the same sample, five points are measured, and the fivewater mobility values are averaged, thereby defining an average valuethereof as a water mobility value of the sample.

In the invention, the water mobility value (0 to 100) is preferably from0.01 to 20, more preferably from 0.01 to 18, further preferably from0.01 to 15, still further preferably from 0.01 to 13, even furtherpreferably from 1 to 13, and even still further preferably from 3 to 13.

A heat generating composition having a water mobility value of less than0.01 is insufficient in moldability. A heat generating compositionhaving a water mobility value of from 0.01 to 50 has moldability andtherefore, is a moldable heat generating composition. When the watermobility value exceeds 20, it is necessary that a part of water of theheat generating composition is removed by water absorption, dehydration,etc. That is, unless a part of water in the heat generating compositionmolded body is removed by water absorption, dehydration, etc. using awater absorptive packaging material, etc., a practical useful exothermicreaction is not caused. Incidentally, in the case where a waterabsorptive polymer having a low water absorption speed is used andalthough a high water mobility value is exhibited at the time ofmolding, after elapsing a certain period of time, a part of surpluswater is taken in the water absorptive polymer, whereby the heatgenerating composition becomes in an exothermic state with a watermobility value of from 0.01 to 20, even a heat generating compositionhaving a high water mobility value is dealt as a heat generatingcomposition in which surplus water does not function as a barrier layer.In a heat generating composition having a water mobility value exceeding50, surplus water is too much, the heat generating composition becomesin a slurry state and loses moldability, and the surplus water functionsas a barrier layer. Thus, even upon contact with air as it is, anexothermic reaction is not caused.

Furthermore, the “water mobility value” as referred to herein is a valueobtained by digitizing surplus water which is the water content capableof being easily and freely oozed out the system in water which iscontained in the heat generating composition or mixture or the like. Ina mixture in which some components of the heat generating composition ormixture or the like are mixed, the amount of the surplus water isvariously changed depending the amount of a component having a waterretaining ability such as a water retaining agent, a carbon componentand a water absorptive polymer and wettability of each component, andtherefore, it is every difficult to predict the water mobility valuefrom the amount of addition of water. Accordingly, since the amount ofsurplus water of the heat generating composition or mixture of the likeis determined from the water mobility value, by determining the amountof addition of water and the amount of other components, a heatgenerating composition or mixture or the like having a substantiallyfixed amount of surplus water is obtained with good reproducibility.That is, by previously examining the water mobility value and acomposition ratio of a heat generating composition or mixture or thelike, a heat generating composition or mixture or the like as compoundedalong that composition ratio has a water mobility value falling within afixed range, namely, an amount of surplus water falling within a fixedrange. Thus, it is possible to easily produce a variety of heatgenerating compositions such as a powdered heat generating compositionwhich causes heat generation upon contact with air but does not havemoldability, a heat generating composition which causes heat generationupon contact with air and has moldability, and a heat generatingcomposition which, after discharging out a fixed amount of surplus waterfrom the system by water absorption, etc., causes heat generation uponcontact with air and has moldability. Accordingly, if the water mobilityvalue is known, it is possible to note what state does the subject heatgenerating composition or mixture or the like take.

If the water mobility value is employed, it is possible to embody adesired state with good reproducibility by a simple measurement. Thus,it becomes possible to determine a component ratio of the heatgenerating composition on the basis of the water mobility value obtainedby the measurement and the component ratio, thereby simply achievingactual production of a heat generating composition.

As a use example of the water mobility value, water (or a reactionaccelerator aqueous solution) is added to and mixed with a mixture ofspecified amounts of heat generating composition components exclusive ofwater (or a reaction accelerator aqueous solution), thereby producingplural heat generating compositions having a different water content.Next, a water mobility value of each of the heat generating compositionsis measured, thereby determining a relationship between the amount ofaddition of water (or a reaction accelerator aqueous solution) and awater mobility value.

A heat generating composition which has moldability and causes heatgeneration upon contact with air has a water mobility value of from 0.01to 20. By determining a compounding ratio of the respective componentstherefrom to prepare a mixture in this compound ratio, a moldable heatgenerating composition in which water does not function as a barrierlayer and which has moldability causes heat generation upon contact withair can be produced with good reproducibility.

In this way, since surplus water is used as a connecting substance and aflocculant aid or a dry binding material is not used, reactionefficiency of the iron powder does not drop. Thus, an exothermicperformance can be obtained in a small amount as compared with the caseof using a flocculant aid or a dry binding material.

Incidentally, in the invention, what water does not function as abarrier layer and causes an exothermic reaction upon contact with airmeans that water in a heat generating composition does not function as abarrier layer which is an air intercepting layer and immediately afterthe production of a heat generating composition, comes into contact withair, thereby immediately causing an exothermic reaction.

By using a moldable heat generating composition containing this surpluswater as a connecting substance, it becomes possible to produce, forexample, a super thin and super flexible heat generating body havingplural sectional exothermic parts of a heat generating compositionmolded body on a substantially planar substrate in a maximum width ofpreferably from 1 to 50 mm, and more preferably from 1 to 20 mm, or in amaximum diameter of preferably from 1 to 50 mm, and more preferably from1 to 20 mm (in the case where two or more axes are present as in anellipse, the major axis is dealt as a length, while the minor axis isdealt as a width).

The “surplus water” as referred to herein means water or an aqueoussolution portion which is present excessively in the heat generatingcomposition and easily transfers to the outside of the heat generatingcomposition. The surplus water is defined as a water mobility valuewhich is a value of water or a value of an aqueous solution portionsucked out from the heat generating composition, etc. by a filter paper.When the heat generating composition has an appropriate amount ofsurplus water, it is assumed that the surplus water causes hydrationagainst hydrophilic groups in the components of the heat generatingcomposition due to a bipolar mutual action or hydrogen bond, etc. andthat it is present even in the surroundings of hydrophobic groups whilehaving high structural properties.

This is connecting water as a connecting substance in some meaning.Besides, there is water in a state called as free water which can freelymove. When the surplus water increases, the structure is softened, andthe free water is found.

The “moldability” as referred to in the invention exhibits that a moldedbody of the heat generating composition having a cavity or concave dieshape is formed by force-through molding using a trimming die having acavity or cast molding using a concave die, whereby after moldingincluding mold release, the molding shape of the heat generatingcomposition molded body is held.

When the moldability is revealed, since the shape is held until the heatgenerating composition molded article is at least covered by a coveringmaterial and a seal part is formed between the substrate and thecovering material, sealing can be achieved in the periphery of the shapewith a desired shape. Also, since so-called “spots” which are acollapsed piece of the heat generating composition are not scattered inthe seal part, the sealing can be achieved without causing cutting inseal. The presence of the spots causes insufficient sealing.

1) Measurement Device:

With respect to the measurement device, a stainless steel-made moldingdie (a plate having a size of 2 mm in thickness×200 mm in length×200 mmin width and having a cavity as treated by R5 in four corners of 60 mmin length×40 mm in width in a central part thereof) and a fixableleveling plate are disposed above a travelable endless belt, and magnets(two magnets having a size of 12.5 mm in thickness×24 mm in length×24 mmin width are disposed in parallel) are disposed under the endless belt.

The magnets should cover a region of the leveling plate and the vicinitythereof and a region larger than a region covered by a cut side (40 mm)vertical to the advancing direction of the cavity of the molding die.

2) Measurement Method:

With respect to the measurement method, a stainless steel plate having asize of 1 mm in thickness×200 mm in length×200 mm in width is placed onthe endless belt of the measurement device, a polyethylene film having asize of 70 μm in thickness×200 mm in length×200 mm in width is placedthereon, and a stainless steel-made molding die is further placedthereon.

Thereafter, a leveling plate is fixed in a position of the cavity of themolding die of 50 mm far from the end portion in the advancing directionof the endless belt, 50 g of a heat generating composition is thenplaced in the vicinity of the leveling plate between the leveling plateand the cavity, and the heat generating composition is filled in thecavity of the molding die while leveling it by moving the endless beltat 1.8 m/min. After the molding die has completely passed through theleveling plate, the traveling of the endless belt is stopped. Next, themolding die is removed, and a heat generating composition molded body aslaminated on the polyethylene film is observed.

3) Judgment Method:

With respect to the judgment method, in the surroundings of the heatgenerating composition molded body, in the case where any collapsedpiece of the heat generating composition molded body exceeding a maximumlength of 800 μm is not present and the number of collapsed pieces ofthe heat generating composition molded body having a maximum length offrom 300 to 800 μm is not more than 5, it is to be noted that the heatgenerating composition has moldability.

The moldability is an essential property for a heat generatingcomposition to be used in the molding system. If the heat generatingcomposition does not have moldability, it is impossible to produce aheat generating body by the molding system.

The “adjustment of the water content” as referred to herein means thatafter contact treating the heat generating mixture with an oxidizinggas, water or an aqueous solution of a reaction accelerator is added.Although the amount of addition of water or an aqueous solution of areaction accelerator is not limited, examples thereof include theaddition of a weight corresponding to a reduced weight by the contacttreatment and the addition of a weight such that a desired watermobility value is obtained.

Whether or nor the adjustment of the water content is introduced may beproperly determined depending upon the utility.

A method for measuring a temperature rise of the heat generatingcomposition is as follows.

1) A heat generating composition is allowed to stand in a state that itis sealed in an air-impermeable outer bag for one hour under a conditionthat the circumferential temperature is 20±1° C.

2) A magnet is provided in the vicinity of a central part of the backside of a polyvinyl chloride-made supporting plate (3 mm inthickness×600 mm in length×600 mm in width) of a footed supporting tableso as to cover a cavity shape of a molding die.

3) A temperature sensor is placed on the central part of the supportingplate.

4) A polyethylene film (25 μm in thickness×250 mm in length×200 mm inwidth) as provided with an adhesive layer having a thickness of about 80μm is stuck onto the supporting plate via a sticky layer such that thecenter of the polyethylene film is positioned at the sensor.

5) The heat generating composition is taken out from the outer bag.

6) A template (250 mm in length×200 mm in width) having a cavity (80 mmin length×50 mm in width×3 mm in height) is placed above the centralpart of the polyethylene film; a sample is placed in the vicinity of thecavity; a force-in die plate is moved along the template; the sample ischarged into the cavity while stuffing; and the sample is leveled whilestuffing along the template plane (force-in die molding), therebyfilling the sample in the die. Next, the magnet beneath the supportingplate is removed, and the temperature measurement is started.

With respect to the measurement of the exothermic temperature, thetemperature is measured for 10 minutes at a measurement timing of 2seconds using a data collector, and exothermic rising properties arejudged in terms of the temperature after elapsing 3 minutes.

The heat generation test of the heat generating body follows the JIStemperature characteristic test.

The “contact treatment with an oxidizing gas” as referred to herein is amethod in which a mixture or heat generating composition havingcomponents of the heat generating composition mixed therein is broughtinto continuous or intermittent contact with an oxidizing gas (forexample, oxygen and air) in an oxidizing gas atmosphere or by blowing anoxidizing gas or other means, thereby partially oxidizing the ironcomponent. A method for determining a degree of oxidation is notlimited. Examples thereof include a method in which a degree of contactof the mixture or heat generating composition with an oxidizing gas isdetermined by the water mobility value of the mixture or heat generatingcomposition, the contact time with the oxidizing gas, the exothermictemperature rise rate at the time of contact, the exothermic temperatureat the time of contact, the maximum exothermic temperature at the timeof contact, a prescribed temperature as dropped after reaching themaximum exothermic temperature at the time of contact, or a combinationthereof, thereby determining a degree of oxidation.

For examples, the following methods are preferable.

(1) A heat generating composition having a water mobility value of notmore than 20 (for example, less than 0.01 or from 0.01 to 20) is exposedto air while fluidizing by stirring or the like to cause self heatgeneration, intercepted from air for a desired period of time until thetemperature exceeds a maximum exothermic temperature and then returnedto room temperature, thereby forming a heat generating composition. Inparticular, a contact treatment with an oxidizing gas by exposing a heatgenerating mixture or heat generating composition having a watermobility value of less than 0.01 to air while stirring, thereby causingself heat generation is preferable.

(2) A heat generating composition having a water mobility valueexceeding 20 is brought into contact with air and intercepted from airfor a desired period of time, thereby forming a heat generatingcomposition.

(3) Water or a reaction accelerator aqueous solution is added to theheat generating composition as obtained in either one of (1) or (2), andthe water content of the mixture is adjusted, followed by mixing to forma heat generating composition having a desired water mobility value. Theweight of the water or reaction accelerator aqueous solution to be addedfor the purpose of adjusting the water content is not limited. Examplesthereof include a weight as reduced against the weight of the mixture orheat generating composition prior to exposing to air, namely prior tocausing self heat generation, or a weight corresponding to the weightexceeding it. If desired, the temperature state of the mixture and theheat generating composition may be controlled prior to the contacttreatment and/or at the time of contact treatment by warming themixture, warming the heat generating composition and warming a reactionvessel, heat insulation, cooling, or a combination thereof. In this way,a heat generating composition having remarkably excellent exothermicrising properties can be obtained.

As the “oxidizing gas” as referred to herein, any substance may beemployed so far as it is gaseous and oxidizing. Examples thereof includean oxygen gas, air, and a mixed gas of an inert gas (for example, anitrogen gas, an argon gas, and a helium gas) and oxygen. As the mixedgas, it is preferable that it contains 10% or more of an oxygen gas. Ofthese, air is especially preferable.

So far as the atmosphere of the contact treatment region does not becomedeficient in oxygen and an oxidation reaction of the iron component iscaused, a temperature of the oxidizing gas, a temperature of the contacttreatment and a time of the contact treatment are not limited and may beproperly determined depending upon the desire. The temperature of theoxidizing gas is preferably from 0 to 200° C., more preferably from 10to 150° C., and further preferably from 20 to 100° C.; and the treatmenttime is preferably from one second to 10 minutes, more preferably from 5seconds to 7 minutes, and further preferably from 15 seconds to 5minutes. In the step, it is preferable that the reaction time is short.

The amount of the oxidizing gas to be used may be adjusted dependingupon the kind of the oxidizing gas, the kind and particle size of theiron powder, the water content, the treatment temperature, the treatmentmethod, and the like. In the case of using air, the amount of air ispreferably from 1 to 1,000 liters/min per 200 g of the iron powder underone atmosphere at 100° C. In the case of other oxidizing gas, the amountof the oxidizing gas may be reduced into the concentration of oxygen onthe basis of the case of air.

If desired, an acidic substance or a peroxide may be added at the timeof the contact treatment with an oxidizing gas. Examples of the peroxideinclude hydrogen peroxide and ozone. In the case of carrying out thetreatment with an oxidizing gas in an open system, the treatment may becarried out in a lid-free vessel or in a manner such that an oxidizinggas such as air comes into a vessel through an air-permeable sheet-likematerial such as non-woven fabrics.

The “heat generating mixture” as referred to herein is a materialobtained by subjecting a reaction mixture containing, as essentialcomponents, an iron powder, a carbon component, a reaction acceleratorand water and having a water content of from 1 to 20% by weight and awater mobility value of less than 0.01 to a contact treatment with anoxidizing gas under fluidization, thereby regulating a temperature riseat 1° C. or higher within 10 minutes. So far as some change is caused inthe reaction mixture by the contact treatment with an oxidizing gas, theiron powder is not always required to be oxidized. However, it ispreferable that the iron powder is oxidized. In that case, it ispreferable that the iron powder becomes an active iron powder.

The “amount of wustite” as referred to herein is an amount expressed by% according to the following expression from an integrated intensity ofpeaks of a (110) plane of iron (αFe) and an integrated intensity ofpeaks of a (220) plane of FeO (wustite) by using an X-ray diffractiondevice.[Amount of wustite (%)]=100×KFeO/(KαFe)

KFeO: Integrated intensity of peaks of a (220) plane of FeO (wustite)

KαFe: Integrated intensity of peaks of a (110) plane of iron (αFe)

The “active iron powder” as referred to herein is an iron powder havinga content of wustite of from 5.01 to 50% by weight. Furthermore, in thecase where the active iron powder is prepared by using a mixturecontaining at least any one of an iron powder and other essentialcomponents (for example, a carbon component, a reaction accelerator, andwater) and in the case where the amount of the active iron powder of theiron powder in the heat generating composition of the heat generatingbody is determined, the iron powder is separated from the mixture or theheat generating composition of the heat generating body after thepreparation by using a magnet, etc. and used as a sample; the amount ofwustite is determined by using an X-ray diffraction device; and if theamount of wustite falls within the range of from 2 to 50% by weight, theresulting iron powder is defined to be an active iron powder.

The “heat generating mixture” as referred to herein is a materialobtained by subjecting a reaction mixture containing, as essentialcomponents, an iron powder, a carbon component, a reaction acceleratorand water and having a water content of from 1 to 30% by weight and awater mobility value of less than 0.01 to a contact treatment with anoxidizing gas under fluidization and holding a temperature of thereaction mixture after the contact at 40° C. or higher for 2 seconds ormore. So far as some change in characteristics is caused in the reactionmixture by the contact treatment with an oxidizing gas, the iron powderis not always required to be oxidized. However, it is preferable thatthe iron powder is oxidized. In that case, it is preferable that theiron powder becomes an active iron powder.

Furthermore, in the case where a heat generating body using a heatgenerating composition in which the active iron powder of the inventionis used is required to be stored over a long period of time, by adding ahydrogen formation inhibitor to the heat generating composition, it ispossible to store the heat generating body without causing swelling overa long period of time. After the storage over a long period of time, aheat generating body having excellent initial rising characteristics canbe used.

The heat generating body of the invention is a heat generating bodycapable of generating heat upon contact with oxygen in air, and a heatgenerating body is formed by accommodating the foregoing heat generatingcomposition containing an active iron powder in an air-permeableaccommodating bag. In addition, the heat generating body may have pluralexothermic parts by heat sealing among heat generating compositions.

Furthermore, the heat generating body may be sealed in anair-impermeable accommodating bag for the purpose of storage ortransportation.

Although the production process of the heat generating body is notlimited, the following production processes are enumerated.

1) Filling System:

The filling system is a method for coupling an end of a substrate or apartition part by an adhesive, sewing processing, or an appropriatesystem such a heat seal system to form a bag, filling a heat generatingcomposition in the bag, and then bonding the end of the bag. As aprocess for producing a compartmentalized heat generating body by thefilling system, there is enumerated a continuous formation method inwhich by using a longitudinal substrate and a rotary heat compressioningunit capable of heat sealing a desired partition part and the peripheryof the substrate, the periphery of the longitudinal substrate and anecessary part of the partitioned as disposed opposite to each other viathe heat compression unit are heated sealed, and at the same time, anair-permeable heat generating body is fed into a compartment formed ofspace between the substrates and subjected to a seal treatment, and theformation of a next compartment is started while bonding an end of thebody warmer by this seal treatment.

2) Pocket System:

As disclosed in JP-T-11-508786, the pocket system is a process forproducing a heat generating body in which a pocket is prepared inadvance on a substrate by thermal molding, mechanical embossing, vacuumembossing, or other tolerable means, a heat generating composition andits compressed body, etc. are filled in the pocket, the pocket iscovered by another substrate, and the surroundings of the two substratesare coupled.

3) Molding System:

The molding system is a process for producing a heat generating body inwhich a moldable heat generating composition is molded into a desiredshape by a force-through molding method using a trimming die or a castmolding method using a casting mold, the molded body is laminated on asubstantially planar substrate not having an accommodating pocket, etc.,and another substrate is covered thereon, followed by sealing.

The “force-through molding method” as referred to herein means acontinuous formation method in which by using a molding machine forlaminating a heat generating composition molded body having a trimmingdie shape on a longitudinal substrate by using a trimming die and arotary seal unit capable of covering the laminate by a longitudinalcovering material and sealing (by heat seal, compression seal, or heatcompression seal) a desired sectioned part and the surroundings of thesubstrate and the covering material, the surroundings of the heatgenerating composition molded body and a necessary part of the sectionedpart are heat sealed via the seal unit and subjected to a sealtreatment.

Furthermore, the “cast molding method” as referred to herein means amolding method for laminating a heat generating composition molded bodyon a longitudinal substance by filling in a casting mold having aconcave and transferring it into a substrate.

In the continuous case, there is enumerated a continuous formationmethod in which by using a molding machine for laminating a heatgenerating molding molded body on a longitudinal substrate by filling ina concave and transferring into a substrate by a drum-type body ofrotation and a rotary seal unit capable of covering the laminate by alongitudinal covering material and sealing (by heat seal, compressionseal, or heat compression seal) a desired sectioned part and thesurroundings of the substrate and the covering material, thesurroundings of the heat generating composition molded body and anecessary part of the sectioned part are heat sealed via the seal unitand subjected to a seal treatment.

Furthermore, in producing a heat generating body using the heatgenerating composition of the invention according to the foregoingmethods or other methods, a magnet may be used. By using a magnet, itbecomes possible to easily achieve accommodation of the heat generatingcomposition in a bag or a mold and separation of the molded body fromthe mold, thereby making it easier to mold a heat generating compositionmolded body or produce a heat generating body.

The fixing means is not limited so far as it has capability for fixing athermal packaging body for joint surroundings or a material having anexothermic part to a prescribed part.

As the fixing means, an adhesive layer, a hook and eye, a hook andbutton, a hook and loop fastener such as Velcro, a magnet, a band, astring, and combination thereof can be arbitrarily used.

Incidentally, in the case of a band, fixing means for adjustment may befurther constructed by a combination of a hook and loop fastener and anadhesive layer.

Here, the “hook and loop fastener” as referred to herein has a fasteningfunction by a combination of a loop as a female fastener with a malefastener capable of fastening the female fastener thereto, which isknown as trade names such as Magic Tape (a registered trademark), MagicFastener (a registered trademark), Velcro Fastener, and Hook and LoopTape. Examples of the material having a loop function include non-wovenfabrics and woven fabrics of napped or hole-containing yarns. Such amaterial having a loop function (female fastener function) may becovered on the surface of a paddling forming the band, or the band maybe constructed of such a material itself. Although the hook member whichis the male fastener member is not particularly limited, examplesthereof include hook members formed of a polyolefin based resin (forexample, polyethylene and polypropylene), a polyamide, a polyester, etc.Although the shape of the hook is not particularly limited, a hookhaving a cross-sectional shape such as an I type, an inverted L type, aninverted J type, and a so-called mushroom type is preferable because itis easily hooked by the loop and does not give an extreme stimulus tothe skin. Incidentally, the hook may be adhered to the entire area of afastening tape, and only the hook may be used as a fastening tape whileomitting a tape substrate.

The adhesive layer may contain at least one member selected fromadditional components consisting of a water retaining agent, a waterabsorptive polymer, a pH adjusting agent, a surfactant, an organosiliconcompound, a hydrophobic polymer compound, a pyroelectric substance, anantioxidant, an aggregate, a fibrous material, a moisturizer, afunctional substance, and a mixture thereof.

The adhesive of the invention is classified into a non-hydrophilicadhesive, a mixed adhesive, and a hydrophilic adhesive (for example, agel).

The adhesive constituting the adhesive layer is not limited so far as ithas an adhesive strength necessary for adhering to the skin or clothes.Adhesives of every form such as a solvent based adhesive, an aqueousadhesive, an emulsion type adhesive, a hot melt type adhesive, areactive adhesive, a pressure-sensitive adhesive, a non-hydrophilicadhesive, and a hydrophilic adhesive are employable.

The adhesive layer includes one layer of a non-hydrophilic adhesiveconstituted of the non-hydrophilic adhesive and non-hydrophilic adhesivelayers constituted of the non-hydrophilic adhesive.

It is to be noted that a material whose water absorption properties areimproving by containing a water absorptive polymer or a water retainingagent in the non-hydrophilic adhesive layer is dealt as thenon-hydrophilic adhesive layer.

A hot melt based adhesive may be provided between the hydrophilicadhesive layer and a substrate or a covering material.

Furthermore, in the case where the hydrophilic adhesive is provided in athermal packaging body for joint surroundings, there is no limitation.After seal treating a thermal packaging body for joint surroundings, ahydrophilic adhesive layer may be provided in the thermal packaging bodyfor joint surroundings.

Furthermore, the adhesive layer may or may not have air permeability andmay be properly selected depending upon the utility. With respect to theair permeability, the adhesive layer may be air-permeable as a whole.Examples thereof include an adhesive layer having air permeability as awhole of a region in which an adhesive is partially present and aportion where no adhesive is present is partially present.

In laminating an adhesive on an air-permeable substrate and/or acovering material in a stratiform state as it is, examples of a methodfor keeping its air permeability include a method in which an adhesivelayer is partially laminated by printing or transferring an adhesive,thereby forming a non-laminated part as an air-permeable part; a methodin which an adhesive is transferred in one direction while drawing acircle in a filament-like form or properly moved in the two-dimensionaldirections by transferring in a zigzag manner, whereby a space of thefilament-like adhesive keeps air permeability or moisture permeabilityor the adhesive is foamed; and a method for forming a layer by a meltblow system.

Examples of the adhesive which constitutes the non-hydrophilic adhesivelayer include acrylic adhesives, polyvinyl acetate based adhesives (forexample, vinyl acetate resin based emulsions and ethylene-vinyl acetateresin based holt melt adhesives), polyvinyl alcohol based adhesives,polyvinyl acetal based adhesives, vinyl chloride based adhesives,polyamide based adhesives, polyethylene based adhesives, cellulose basedadhesives, chloroprene (neoprene) based adhesives, nitrile rubber basedadhesives, polysulfide based adhesives, butyl rubber based adhesives,silicone rubber based adhesives, styrene based adhesives (for example,styrene based hot melt adhesives), rubber based adhesives, and siliconebased adhesives. Of these, rubber based adhesives, acrylic adhesives,and adhesives containing a hot melt based polymer substance for thereasons that they are high in the adhesive strength, are cheap, are goodin long-term stability, and are small in reduction of the adhesivestrength even by providing heat.

In addition to the base polymer, if desired, the adhesive may becompounded with other components such as tackifiers (for example,petroleum resins represented by rosins, chroman-indene resins,hydrogenated petroleum resins, maleic anhydride-modified rosins, rosinderivatives, and C-5 based petroleum resins), phenol based tackifiers(especially, tackifiers having an aniline point of not higher than 50°C.; for example, terpene phenol based resins, rosin phenol based resins,and alkylphenol based resins), softeners (for example, coconut oil,castor oil, olive oil, camellia oil, and liquid paraffin), softeners,anti-aging agents, fillers, aggregates, adhesion adjusting agents,adhesion modifiers, coloring agents, anti-foaming agents, thickeners,and modifiers, thereby improving performance such as an improvement inadhesion to nylon-made clothes and mixed yarn clothes.

Examples of the hot melt based adhesive include known hot melt basedadhesives imparted with adhesion. Specific examples thereof includestyrene based adhesives made of, as a base polymer, an A-B-A type blockcopolymer (for example, SIS, SBS, SEBS, and SIPS), vinyl chloride basedadhesives made of, as a base polymer, a vinyl chloride resin, polyesterbased adhesives made of, as a base polymer, a polyester, polyamide basedadhesives made of, as a base polymer, a polyamide, acrylic adhesivesmade of, as a base polymer, an acrylic resin, polyolefin based adhesivesmade of, as a base polymer, a polyolefin (for example, polyethylene,super low density polyethylene, polypropylene, ethylene-α-olefincopolymers, and ethylene-vinyl acetate copolymers), 1,2-polybutadienebased adhesives made of, as a base polymer, 1,2-polybutadiene, andpolyurethane based adhesives made of, as a base polymer, polyurethane;adhesives made of a modified body of the foregoing adhesive whoseadhesion is improved or whose stability is changed; and mixtures of twoor more kinds of these adhesives. Adhesive layers constituted of afoamed adhesive and adhesive layers constituted of a crosslinkedadhesive can also be employed.

The non-aromatic hot melt based adhesive is not limited so far as it ismade of, as a base polymer, a hot melt based adhesive not containing anaromatic ring. Examples thereof include olefin based hot melt basedadhesives and acrylic hot melt based adhesives. As the non-aromaticpolymer which is the base polymer not containing an aromatic ring, thereare enumerated polymers or copolymers of an olefin or a diene. Examplesthereof include olefin polymers. The olefin polymer includes polymers orcopolymers of ethylene or an α-olefin. Also, polymers resulting fromadding a diene (for example, butadiene and isoprene) as other monomerthereto may be employed.

The α-olefin is not limited so far as it is a monomer having a doublebond in the terminal thereof. Examples thereof include propylene,butene, heptane, hexene, and octene.

The “aromatic hot melt based adhesive” as referred to herein is a hotmelt based adhesive whose base polymer contains an aromatic ring.Examples thereof include styrene based hot melt based adhesivesrepresented by A-B-A type block copolymers.

In the foregoing A-B-A type block copolymers, the A block is anon-elastic polymer block made of a monovinyl substituted aromaticcompound A such as styrene and methylstyrene; and the B block is anelastic polymer block made of a conjugated diene such as butadiene andisoprene. Specific examples thereof include a styrene-butadiene-styreneblock copolymer (SBS), a styrene-isoprene-styrene block copolymer (SIS),and hydrogenated types thereof (for example, SEBS and SIPS), andmixtures thereof.

As a countermeasure for preventing a lowering of adhesive strengthcaused due to an increase of water of the non-hydrophilic adhesivelayer, an adhesive layer obtained by further compounding a waterabsorptive polymer in the non-hydrophilic adhesive can be used.

The hydrophilic adhesive which constitutes the hydrophilic adhesivelayer is not particularly limited so far as it contains a hydrophilicpolymer or a water-soluble polymer as the major component, has adhesionand is hydrophilic as an adhesive.

Examples of the constitutional components of the hydrophilic adhesiveinclude hydrophilic polymers (for example, polyacrylic acid),water-soluble polymers (for example, poly(sodium acrylate) andpolyvinylpyrrolidone), crosslinking agents (for example, dry aluminumhydroxide and meta-silicic acid aluminic acid metal salts), softeners(for example, glycerin and propylene glycol), higher hydrocarbons (forexample, soft liquid paraffin and polybutene), primary alcohol fattyacid esters (for example, isopropyl myristate), silicon-containingcompounds (for example, silicone oil), fatty acid glycerin esters (forexample monoglycerides), oily components (for example, vegetable oilssuch as olive oil), antiseptics (for example, methyl p-hydroxybenzoateand propyl p-hydroxybenzoate), solubilizing agents (for example,N-methyl-2-pyrrolidone), thickeners (for example, carboxy-methylcellulose), surfactants (for example, polyoxyethylene hardened castoroil and sorbitan fatty acid esters), hydroxycarboxylic acid (forexample, tartaric acid), excipients (for example, light silicicanhydride, water absorptive polymers, and kaolin), moisturizers (forexample, D-sorbitol), stabilizers (for example, sodium edetate,p-hydroxybenzoic acid esters, and tartaric acid), crosslinking typewater absorptive polymers, boron compounds (for example, boric acid),and water. They may be used as an arbitrary combination.

A temporary adhering seal part is formed via a sticky layer. An adhesivewhich constitutes the sticky layer is a layer formed of a polymercomposition which is tacky at the normal temperature and is not limitedso far as it can be heat sealed after temporary adhesion.

Furthermore, the foregoing adhesives of the sticky layer can be used asthe adhesive which constitutes the sticky layer as used for temporaryadhesion. Of these, non-hydrophilic adhesives are preferable. Withrespect to the adhesive constituting the adhesive layer, it ispreferable that the adhesive is well compatible with a heat sealmaterial constituting a heat seal and that a melting point of the basepolymer of the adhesive is not higher than a melting point of the heatseal material. Hot melt based adhesives are especially preferable forhot melt based bonding agents. Furthermore, in the case where the heatseal material is an olefin based raw material, preferred examplesthereof include olefin based adhesives.

A bonding layer for fixing the air permeability adjusting material isconstituted of a bonding agent or an adhesive which is usually used. Inparticular, an adhesive is useful, and the foregoing adhesives forconstituting the adhesive layer can be used.

Furthermore, a method for providing a bonding layer is not limited sofar as the air permeability adjusting material can be fixed. The bondinglayer may be entirely provided or partially or intermittently provided.Examples of its shape include various shapes such as a network-likeshape, a stripe-like shape, a dot-like shape, and strip-like shape.

Furthermore, in the case where an adhesive layer is employed as thehydrophilic adhesive layer, if there is a difference in a waterretaining force between the hydrophilic adhesive layer and the heatgenerating composition molded body, transfer of water occurs via apackaging material present therebetween such as a substrate, therebycausing in-conveniences against the both. In particular, the transfer ofwater occurs during the storage. In order to prevent this, it ispreferable that the packaging material present therebetween at least hasa moisture permeability of not more than 2 g/m²/day in terms of amoisture permeability according to the Lyssy method. By using this, inthe case where the heat generating body is accommodated in an outer bagas an air-impermeable accommodating bag and stored, the transfer ofwater can be prevented.

In the case where a hydrophilic adhesive layer is used as the adhesivelayer, the moisture permeability of a moisture-proof packaging materialprovided between the heat generating composition molded body and thehydrophilic adhesive layer is not limited so far as the transfer ofwater can be prevented within the range where the exothermic performanceis not affected. The moisture permeability according to the Lyssy methodis usually not more than 2 g/m²/day, preferably not more than 1.0g/m²/day, more preferably not more than 0.5 g/m²/day, and furtherpreferably from 0.01 to 0.5 g/m²/day. These values are a value under acondition under an atmospheric pressure at 40° C. and 90% RH.Incidentally, the moisture-proof packaging material can be used as asubstrate or a covering material and may be laminated singly on asubstrate, a covering material, or the like.

The moisture-proof packaging material is not limited so far as thetransfer of water between the heat generating composition molded bodyand the hydrophilic adhesive layer can be prevented. Examples thereofinclude metal vapor deposited films, vapor deposited films of a metaloxide, metal foil-laminated films, EVOH (ethylene/vinyl alcoholcopolymer or ethylene/vinyl acetate copolymer saponified product) basedfilms, biaxially stretched polyvinyl alcohol films, polyvinylidenechloride coated films, polyvinylidene chloride coated films obtained bycoating polyvinylidene chloride on a substrate film (for example,polypropylene), metal foils such as an aluminum foil, air-impermeablepackaging materials obtained by vapor depositing or sputtering a metal(for example, aluminum) on a polyester film substrate, and packaginglaminates using a transparent barrier film of a structure in whichsilicon oxide or aluminum oxide is provided on a flexible plasticsubstrate. The air-impermeable packaging materials which are used in theouter bag, etc. can also be used.

Furthermore, packaging materials such as moisture-proof packagingmaterials as described in JP-A-2002-200108, the disclosures of which canbe incorporated herein by reference, can be used.

In the case of using a water-containing hydrophilic adhesive (forexample, a gel) in the adhesive layer, in order to adjust the moistureequilibrium between the heat generating composition and the adhesivelayer, the content of a reaction accelerator (for example, sodiumchloride) or a substance having a water holding power (for example, awater absorptive polymer) in the heat generating composition may beadjusted within the range of from 10 to 40% by weight, preferably from15 to 40% by weight, and more preferably from 15 to 30% by weight basedon the heat generating composition.

Furthermore, as the adhesive having good moisture permeability and lowstimulation to the skin, water-containing adhesives (for example,hydrophilic adhesives and gels) as described in JP-A-10-265373 andJP-A-9-87173, adhesives which can be subjected to hot melt coating asdescribed in JP-A-6-145050 and JP-A-6-199660, and rubber based adhesivesas described JP-A-10-279466 and JP-A-10-182408, the disclosures of whichare totally incorporated herein by reference, are useful.

The water retaining agent is not limited so far as it is able to retainwater. Examples thereof include porous materials derived from plantshaving high capillary function and hydrophilicity such as wood meal,pulp powder, active carbon, sawdust, cotton cloth having a number ofcotton fluffs, short fiber of cotton, paper dust, and vegetablematerials, water-containing magnesium silicate based clay minerals suchas active clay and zeolite, pearlite, vermiculite, silica based poroussubstances, coralline stone, and volcanic ash based substances (forexample, terraballoon, shirasu balloon, and taisetsu balloon). In orderto increase a water retaining ability and enhance a shape holdingability of such a water retaining agent, the water retaining agent maybe subjected to a processing treatment such as baking and/orpulverization.

The water absorptive polymer is not particularly limited so far as it isa resin having a crosslinking structure and having a water absorptionmagnification of ion-exchanged water of 3 times or more of the deadweight. Furthermore, a water absorptive polymer the surface of which iscrosslinked may be employed. Conventionally known water absorptivepolymers and commercial products may also be employed.

Examples of the water absorptive polymer include poly(meth)acrylic acidcrosslinked materials, poly(meth)-acrylic acid salt crosslinkedmaterials, sulfonic group-containing poly(meth)acrylic ester crosslinkedmaterials, polyoxyalkylene group-containing poly(meth)acrylic estercrosslinked materials, poly(meth)acrylamide crosslinked materials,crosslinked materials of a copolymer of a (meth)acrylic acid salt and a(meth)acrylamide, crosslinked materials of a copolymer of ahydroxyalkyl(meth)acrylate and a (meth)acrylic acid salt, polydioxolanecrosslinked materials, crosslinked polyethylene oxide, crosslinkedpolyvinylpyrrolidone, sulfonated polystyrene crosslinked materials,crosslinked polyvinylpyridine, saponification products of astarch-poly(meth)acrylonitrile graft copolymer, starch-poly(meth)acrylicacid (salt) graft crosslinked copolymers, reaction products of polyvinylalcohol and maleic anhydride (salt), crosslinked polyvinyl alcoholsulfonic acid salts, polyvinyl alcohol-acrylic acid graft copolymers,and polyisobutylene maleic acid (salt) crosslinked polymers. These waterabsorptive polymers may be used alone or in combination with two or morekinds thereof.

Of these water absorptive polymers, water absorptive polymers havingbiodegradation properties are not limited so far as they are abiodegradable water absorptive polymer. Examples thereof includepolyethylene oxide crosslinked materials, polyvinyl alcohol crosslinkedmaterials, carboxymethyl cellulose crosslinked materials, alginic acidcrosslinked materials, starch crosslinked materials, polyamino acidcrosslinked materials, and polylactic acid crosslinked materials.

The pH adjusting agent is not limited so far it is able to adjust thepH. Examples thereof include alkali metal weak acid salts and hydroxidesand alkaline earth metal weak acid salts and hydroxides such as Na₂CO₃,NaHCO₃, Na₃PO₄, Na₂HPO₄, Na₅P₃O₁₀, NaOH, KOH, Ca(OH)₂, Mg(OH)₂, andCa₃(PO₄)₂.

The surfactant includes anionic surfactants, cationic surfactants,nonionic surfactants, and ampholytic surfactants. Especially, nonionicsurfactants are preferable, and examples thereof include polyoxyethylenealkyl ethers, alkylphenol ethylene oxide adducts, and higher alcoholphosphoric acid esters.

The organosilicon compound is not limited so far as it is a compoundhaving at least an Si—O—R bond and/or an Si—N—R bond and/or an Si—Rbond. The organosilicon compound is in the form of a monomer, a lowlycondensed product, a polymer, etc. Examples thereof include organosilanecompounds such as methyltriethoxysilane; and dimethylsilicone oil,polyorganosiloxane, or silicone resin compositions containing the same.

The hydrophobic polymer compound is not limited so far as it is apolymer compound having a contact angle with water of 40° or more,preferably 50° or more, and more preferably 60° or more in order toimprove the draining in the composition. The shape of the hydrophobicpolymer compound is not limited, and examples thereof include powdery,particulate, granular, and tablet shapes. Examples of the hydrophobicpolymer compound include polyolefins such as polyethylene andpolypropylene, polyesters, and polyamides.

The pyroelectric substance is not limited so far as it haspyroelectricity. Examples thereof include tourmaline, hemimorphic ores,and pyroelectric ores. Tourmaline or achroite which is a kind oftourmaline is especially preferable. Examples of the tourmaline includedravite, schorl, and elbaite.

The aggregate is not limited so far as it is useful as a filler and/oris useful for making the heat generating composition porous. Examplesthereof include fossilized coral (for example, coral fossil andweathered coral fossil), bamboo charcoal, bincho charcoal,silica-alumina powders, silica-magnesia powders, kaolin, crystallinecellulose, colloidal silica, pumice, silica gel, silica powders, micapowders, clays, talc, synthetic resin powders or pellets, foamedsynthetic resins such as foamed polyesters or polyurethanes,diatomaceous earth, alumina, and cellulose powder. Incidentally, it isto be noted that kaolin and crystalline cellulose are not contained inthe heat generating composition of the invention.

The fibrous material is an inorganic fibrous material and/or an organicfibrous material. Examples thereof include rock wool, glass fibers,carbon fibers, metal fibers, pulps, papers, non-woven fabrics, wovenfabrics, natural fibers such as cotton and hemp, regenerated fibers suchas rayon, semi-synthetic fibers such as acetates, synthetic fibers, andpulverized products thereof.

The moisturizer is not limited so far as it is able to hold moisture.Examples thereof include hyaluronic acid, collagen, glycerin, and urea.

The functional substance is not limited so far as it has any function.Examples thereof include at least one kind selected from aromaticcompounds, vegetable extracts, crude drugs, perfumes, slimming agents,analgesics, blood circulation promoters, swelling improvers,antibacterial agents, sterilizers, mold inhibitors, odor eaters,deodorants, percutaneously absorptive drugs, fat-splitting components,minus ion generators, far infrared ray radiants, magnetic bodies,fomentations, cosmetics, bamboo vinegar, and wood vinegar.

Specific examples thereof include aromatic compounds (for example,menthol and benzaldehyde), vegetable extracts (for example, mugwortextract), crude drugs (for example, moxa), perfumes (for example,lavender and rosemary), slimming agents (for example, aminophylline andtea extract), analgesic drugs (for example, indomethacin anddl-camphor), blood circulation promoters (for example, acidicmucopolysaccharide and chamomile), swelling improvers (for example,horse chestnut extract and flavone derivatives), fomentations (forexample, aqueous boric acid, physiological saline, and aqueousalcohols), fat-splitting components (for example, jujube extract,caffeine, and tonalin), cosmetics (for example, aloe extracts, vitaminpreparations, hormone preparations, anti-histamines, and amino acids),antibacterial agents and sterilizers (for example, carbolic acidderivatives, boric acid, iodine preparations, invert soaps, salicylicacid based substances, sulfur, and antibiotics), and mold inhibitors.

The percutaneously absorptive drug is not particularly limited so far asit has percutaneous absorption. Examples thereof includecorticosteroids, anti-inflammatory drugs, hypertension drugs,anesthetics, hypnotic sedatives, tranquilizers, antibacterialsubstances, antifungal substances, skin stimulants, inflammationinhibitors, anti-epileptics, analgesics, antipyretics, anesthetics, moldinhibitors, antimicrobial antibiotics, vitamins, antiviral agents,swelling improvers, diuretics, antihypertensives, coronary vasodilators,anti-tussive expectorants, slimming agents, anti-histamines,antiarrhythmic agents, cardiotonics, adrenocortical hormones, bloodcirculation promoters, local anesthetics, fat-splitting components, andmixtures thereof. However, it should not be construed that the inventionis limited thereto. These drugs are used singly or in admixture of twoor more kinds thereof as the need arises.

The content of such a functional substance is not particularly limitedso far as it falls within the range where the effect of a medicine canbe expected. However, from the viewpoints of adhesive strength as wellas pharmacological effect and economy, the content of the functionalsubstance is preferably from 0.01 to 25 parts by weight, and morepreferably from 0.5 to 15 parts by weight based on 100 parts by weightof the adhesive.

Furthermore, a method for providing the adhesive layer is not limited sofar as a thermal packaging body for joint surroundings can be fixed. Theadhesive layer may be entirely provided or partially or intermittentlyprovided. Examples of its shape include various shapes such as anetwork-like shape, a stripe-like shape, a dot-like shape, andstrip-like shape.

The heat generating body of the invention is able to give variousshapes, thicknesses and temperature zones and therefore, can be used forvarious utilities such as use for a joint, facial esthetic use, use foreyes, slimming use, use for heating or warming a dripping solution, usefor a wet compress pack, use for a medical body warmer, use for a neck,use for a waist, use for a mask, use for a glove, use for hemorrhage,use for relaxation of symptoms such as shoulder pain, muscular pain, andmenstrual pain, use for a cushion, use for heating or warming a humanbody during the operation, use for a thermal sheet, use for thermallyvolatilizing an aroma, use for an abdomen, insecticidal use by thermalvolatilization, and use for treating cancer in addition to commonwarming of a human body. In addition, the heat generating body of theinvention can be used for heating or warming machines, pets, etc.

For example, in the case of using for relaxation of symptoms, the heatgenerating body of the invention is applied directly in a necessary siteof the body or indirectly via a cloth, etc. Furthermore, in the case ofusing for heating or warming a human body during the operation, a methodfor using the heat generating body of the invention includes thefollowing methods.

(1) The heat generating body is directly applied to a body requiringheating or warming.

(2) The heat generating body is fixed on a covering, etc. and covered onthe body.

(3) The heat generating body is fixed on a cushion to be placed beneaththe body, etc.

(4) The heat generating body is used as a covering or a cushion which isa product having the heat generating body provided therein in advance.

Incidentally, examples of the pain of muscles or bones include acutemuscle pain, acute bone pain, acute reference pain, previous musclepain, previous bone pain, chronic reference pain, and join pain of knee,elbow, etc.

The holding time is not limited but is preferably from 20 seconds to 24hours, more preferably from one hour to 24 hours, and further preferablyfrom 8 hours to 24 hours.

The holding temperature is preferably from 30 to 50° C., more preferablyfrom 32 to 50° C., further preferably from 32 to 43° C., still furtherpreferably from 32 to 41° C., and even further preferably from 32 to 39°C.

The invention will be specifically described below with reference to theExamples. Next, the invention will be specifically described withreference to the Examples, but it should not be construed that theinvention is limited thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] is a plan view of an embodiment of the heat generating body ofthe invention.

[FIG. 2] is a cross-sectional view along the line Z-Z of the same.

[FIG. 3] is a diagram of exothermic characteristics of the heatgenerating composition of Example 1 and Comparative Example 1.

[FIG. 4] is a diagram of exothermic characteristics of the heatgenerating body of Examples 2 and Comparative Example 2.

[FIG. 5] is a plan view of another embodiment of the heat generatingbody of the invention.

[FIG. 6] is a plan view of a filter paper for the measurement of watermobility value in the invention.

[FIG. 7] is an oblique view for explaining the measurement of watermobility value in the invention.

[FIG. 8] is a cross-sectional view for explaining the measurement ofwater mobility value in the invention.

[FIG. 9] is a cross-sectional view for explaining the measurement ofwater mobility value in the invention.

[FIG. 10] is a plan view of a filter paper after carrying out themeasurement of water mobility value in the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   1: Heat generating body    -   1C: Sectioned part (seal part)    -   2: Heat generating composition molded body    -   2′: Heat generating composition molded body (sectional        exothermic part)    -   3: Substrate    -   4: Covering material    -   8: Perforation    -   9: Pushing plate    -   10: Flat plate    -   11: Non-water absorptive film (polyethylene film, etc.)    -   12: Filter paper in which eight lines are drawn radiating from        the central point with an interval of 45°    -   13: Die plate    -   14: Hole    -   15: Sample    -   16: Stainless steel plate    -   17: Distance to the oozed-out locus of water or aqueous solution    -   18: Position corresponding to a hollow cylindrical hole on        filter paper

EXAMPLES Example 1

A stirring type batchwise oxidizing gas contact treatment deviceconsisting of a mixer equipped with a rotary blade for stirring was usedas an oxidizing gas contact treatment device, and air was used as anoxidizing gas. First of all, a reaction mixture consisting of 100 partsby weight of a reduced iron powder (particle size: not more than 300μm), 3.0 parts by weight of active carbon (particle size: not more than300 μm), and 10 parts by weight of 11% salt water and having a watermobility value of less than 0.01 was charged in the stirring typebatchwise oxidizing gas contact treatment device. Next, in the statethat the upper portion of the oxidizing gas contact treatment device wasopened to air, the reaction mixture was subjected to self heatgeneration with stirring under circumstances at 20° C. and contacttreated with an oxidizing gas at a maximum exothermic temperature of 68°C. until the exothermic temperature reached 35° C., thereby obtaining acontact treated reaction mixture. With respect to the iron powder of thecontact treated reaction mixture, an integrated intensity ratio wasdetermined from an integrated intensity of peaks (at 58.28, 64.92 and82.22 (2θ/deg)) of a (110) plane of iron (αFe) and an integratedintensity of peaks (at 35.24, 41.59, 60.95, 72.70 and 76.51 (2θ/deg)) ofa (220) plane of FeO (wustite) by using an X-ray diffraction device,from which was then determined an amount of wustite.

The amount of wustite of the reaction mixture was 10%.

Then, 11% salt water was mixed in the foregoing contact treated reactionmixture to obtain a heat generating composition having a water mobilityvalue of 10.

Comparative Example 1

A heat generating composition having a water mobility value of 10 wasprepared in the same manner as in Example 1, except that the contacttreatment with an oxidizing gas was not carried out.

Each of the heat generating compositions as obtained in Example 1 andComparative Example 1 was subjected to an exothermic test, therebyobtaining the results as shown in FIG. 3. Comparative Example 1 wasdeteriorated in exothermic rising properties.

Example 2

A stirring type batchwise oxidizing gas contact treatment deviceconsisting of a mixer equipped with a rotary blade for stirring was usedas an oxidizing gas contact treatment device, and air was used as anoxidizing gas. First of all, a reaction mixture consisting of 100 partsby weight of a reduced iron powder (particle size: not more than 300μm), 5.2 parts by weight of active carbon (particle size: not more than300 μm), 2.3 parts by weight of a wood meal (particle size: not morethan 300 μm), 2.3 parts by weight of a water absorptive polymer(particle size: not more than 300 μm), 0.2 parts by weight of calciumhydroxide, 0.7 parts by weight of sodium sulfite, and 10 parts by weightof 11% salt water and having a water mobility value of less than 0.01was charged in the stirring type batchwise oxidizing gas contacttreatment device. Next, in the state that the upper portion of theoxidizing gas contact treatment device was opened to air, the reactionmixture was subjected to self heat generation with stirring undercircumstances at 20° C. and contact treated with an oxidizing gas at amaximum exothermic temperature of 68° C. until the exothermictemperature reached 35° C., thereby obtaining a contact treated reactionmixture. With respect to the iron powder of the contact treated reactionmixture, an integrated intensity ratio was determined from an integratedintensity of peaks of a (110) plane of iron (αFe) and an integratedintensity of peaks of a (220) plane of FeO (wustite) by using an X-raydiffraction device, from which was then determined an amount of wustite.The amount of wustite of the reaction mixture was 10%. Next, 11% saltwater was mixed in the foregoing contact treated reaction mixture toobtain a heat generating composition having a water mobility value of 8.

This heat generating composition was subjected to an exothermic test ofheat generating composition. As a result, the temperature reached about50° C. (an average value of five samples) after 3 minutes.

Furthermore, the heat generating composition was tested for moldability.As a result, even after separating a trimming die from a heat generatingcomposition molded body, the heat generating composition molded body wasfree from a loss of shape, and collapsed pieces of the heat generatingcomposition molded body were not generated in the surroundings of theheat generating composition molded body.

Next, as illustrated in FIGS. 1 and 2, by using the heat generatingcomposition of Example 2, a heat generating composition molded body 2was laminated on a polyethylene film 3A of an air-impermeable substrate3 in which an adhesive layer 3B provided with a separator 3C wasprovided on the polyethylene film 3A by a trimming die having arectangular cavity of 2 mm in thickness, 110 mm in length and 80 mm inwidth. In addition, an air-permeable covering material 4 made of alaminate of a nylon-made non-woven fabric 4A and a porous film 4B wassuperimposed thereon such that the surface of the polyethylene film 3Aand the surface of the porous film 4B were brought into contact witheach other. The surroundings were heat sealed in a seal width of 8 mmand then cut to produce a rectangular flat heat generating body 1 of 130mm in length, 100 mm in width and 8 mm in seal width.

Even after separating the trimming die from the heat generatingcomposition molded body 2, the laminate was free from a loss of shape,and collapsed pieces of the heat generating composition molded body 2were not generated in the surroundings of the heat generatingcomposition molded body 2. Also, sealing could be completely carried outwithout causing incorporation of collapsed pieces of the heat generatingcomposition molded body 2 into the seal part, and seal failure did notoccur. Incidentally, the air permeability of the covering material 4 was370 g/m²/24 hr in terms of a moisture permeability by the Lyssy method.

Next, the heat generating body was sealed and accommodated in anair-impermeable outer bag and then allowed to stand at room temperaturefor 24 hours.

After 24 hours, the heat generating body was taken out from the outerbag and subjected to an exothermic test by the body. As a result, it wasfelt warm after 3 minutes, and thereafter, the warmth was continued for10 hours or more.

Comparative Example 6

A heat generating composition was obtained in the same manner as inExample 2, except that the contact treatment with an oxidizing gas wasnot carried out, from which was then obtain a heat generating body. Theheat generating body was subjected to an exothermic test by the body. Asa result, it took 6 minutes until it was felt warm.

With respect to Example 2 and Comparative Example 2, the exothermic testof heat generating body was carried out. As a result, as shown in FIG.4, in the case of Example 2, the temperature was 34° C. after 3 minutesand 37° C. after 10 minutes, respectively. However, in the case ofComparative Example 2, the temperature was 22° C. after 30 minutes and34° C. after 10 minutes, respectively. The heat generating body usingthe heat generating composition of the invention was excellent withrespect to the exothermic rising properties.

Example 3

By using the heat generating composition of Example 2, a heat generatingcomposition molded body 2′ (sectional exothermic part) of a rectangularparallelepiped of 2 mm in thickness, 115 mm in length and 80 mm in widthwas laminated in the side of a polyethylene film of an air-impermeablesubstrate in which an adhesive layer provided with a separator wasprovided on a polyethylene film by force-through molding using atrimming die having a thickness of 2 mm and comprising 9 square cavitieshaving a length of one side of 15 mm as illustrated in FIG. 5. Inaddition, an air-permeable covering material made of a laminate of anylon-made non-woven fabric and a polyethylene-made porous film wassuperimposed thereon such that the surface of the foregoing polyethylenefilm and the surface of the porous film were brought into contact witheach other. The periphery of the heat generating composition molded body2′ (sectional exothermic part) was heat sealed in a seal width of 8 mmto provide a seal part 1C, from which was then produced a rectangularirregular heat generating body 1 of 135 mm in length, 100 mm in widthand 8 mm in seal width. Incidentally, in FIG. 5, the numeral 8represents a perforation from which cutting by hand is possible.Furthermore, the air permeability of the covering material was 370g/m²/24 hr in terms of a moisture permeability by the Lyssy method. Theheat generating body was sealed and accommodated in an air-impermeableouter bag and then allowed to stand at room temperature for 24 hours. Asa result of an exothermic test by the body, it was felt warm after 3minutes, and thereafter, the warmth was continued for 10 hours or more.

1. An active iron powder to be contained in a heat generatingcomposition capable of generating heat upon contact with air,characterized in that an amount of wustite to be contained in an ironpowder is from 5.01 to 50% by weight in terms of an X-ray peak intensityratio to iron.
 2. The active iron powder according to claim 1,characterized in that the active iron powder is at least one memberselected from a reduced iron powder, an atomized iron powder, and aniron powder comprising particles, a surface of each of which is at leastpartially covered by a conductive carbonaceous substance.
 3. A heatgenerating composition containing as essential components containing aniron active powder according to claim 1, a carbon component, a reactionaccelerator and water, characterized in that the active iron powderaccounts for from 30 to 100% by weight of the iron powder in the heatgenerating composition.
 4. A heat generating body, characterized bycontaining the heat generating composition according to claim
 3. 5. Theheat generating body according to claim 4, characterized in that theheat generating body has fixing means in at least a part thereof.
 6. Theheat generating body according to claim 5, characterized in that thefixing means is an adhesive layer; and that the adhesive layer containsat least one member selected from additional components consisting of awater retaining agent, a water absorptive polymer, a pH adjusting agent,a surfactant, an organosilicon compound, a hydrophobic polymer compound,a pyroelectric substance, an antioxidant, an aggregate, a fibrousmaterial, a moisturizer, a functional substance, and a mixture thereof.